Isoelastic Monoblock vs Modular Press-Fit Cup
As the volume of total hip arthroplasty (THA) cases continues to rise, so too will the need for revision surgery. Revision THA can be complicated by insufficient bone stock on either the femoral or acetabular side, and researchers are gaining further insight into bone loss potentially related to implant design, such as loss that may occur through stress-shielding from press-fit implants.
In a randomized controlled trial recently reported in JBJS, Brodt et al. evaluated reduction in bone mineral density (BMD), primarily periacetabular BMD, as measured in 2 groups: patients who received a press-fit isoelastic monoblock cup (24 patients analyzed) and those who received a modular titanium press-fit cup (23 patients analyzed). At question was whether an isoelastic monoblock cup, with an elastic modulus similar to that of bone, would lead to less stress-shielding and thus less bone loss compared with a conventional modular titanium cup.
Periprosthetic BMD was assessed at 1 week postoperatively (baseline) and at 4 years postoperatively using dual x-ray absorptiometry (DXA). The authors evaluated 4 regions of interest (ROIs) around the acetabular component and 7 ROIs around the femoral component based on regions previously described in the literature for assessing periprosthetic bone loss.
Baseline patient characteristics, operative time, and improvement in clinical outcome scores did not differ between the groups. A decrease in overall periacetabular BMD was found in both groups, but the difference between the groups was not significant.
However, the researchers found a significant difference between the groups in BMD changes in certain periprosthetic regions. On the acetabular side, the group with the modular titanium cup had a 15.9% decrease in BMD in zone 2 (the superior pole of the acetabulum) compared with a decrease of 4.9% in the group with the isoelastic monoblock cup. And on the femoral side, the group with the modular titanium cup had a 15.4% decrease in BMD in zone 1 (along the greater trochanter) compared with a loss of 7% in the group with the isoelastic monoblock cup. None of the other regions differed significantly between the groups.
Despite the relatively short follow-up and small (but adequately powered) numbers, these results are worthy of our consideration. I agree with the authors that longer follow-up is needed before conclusions can be drawn. As implant design can impact component longevity, it is critical that we evaluate differences to better understand the long-term implications.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Reimbursement for Revision TKA Has Not Kept Pace with Inflation
I was once told that if you don’t have any cases with complications, you either aren’t operating enough or aren’t following your patients. Although we in the orthopaedic community make every effort to minimize the occurrence of patient complications, one that remains difficult to eradicate is periprosthetic joint infection (PJI), which is a leading cause of revision total knee arthroplasty (TKA). The welfare of our patients requires successfully addressing this potentially devastating outcome, but reimbursement for these complex cases has decreased over the past decade.
In the upcoming issue of JBJS, Jella et al. offer insight on temporal trends in Medicare physician reimbursement for revision TKA. They queried the Medicare Physician Fee Schedule Look-Up Tool for pricing information corresponding to 1 and 2-stage revision TKAs and used monetary data from Medicare Administrative Contractors to calculate nationally representative means. The authors evaluated aseptic revision of 1 component, 1-stage revision (aseptic or septic), and both the first and second stages of a 2-stage septic revision.
They found that, from 2002 to 2019, there was a mild increase in the physician fee for each CPT code, with the exception of that for second-stage implantation. However, after adjusting for inflation, total Medicare reimbursements declined for both septic and aseptic revision TKAs (between 23% and 33%), with a significantly greater decline observed for septic revision.
The authors also found that Medicare spending on aseptic revision TKA nearly doubled from 2004 to 2017, while spending on septic revision TKA increased only slightly. They note that a main driver of the discrepancy between septic and aseptic revision may be the reimbursement for the second stage of the former procedure using CPT 27447 instead of a revision procedure code (27487).
We know that an increase in revision TKAs (both septic and aseptic) is expected as the number of primary TKA procedures continues to rise. If reimbursement doesn’t keep pace, it is likely to drive certain surgeons away from tackling the sometimes difficult cases, in turn, leaving our patients with fewer available resources when faced with PJI.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
Life Expectancy Informs Choice of Hemi Implant after Femoral Neck Fracture
Predicting life expectancy is not an exact science. But estimating the remaining years of life in elderly patients with a femoral neck fracture may help orthopaedists determine whether to use unipolar or bipolar hemiarthroplasty components when surgically managing that population. So suggest Farey et al. in the February 3, 2021 issue of The Journal of Bone & Joint Surgery.
The relevant “magic number” for life expectancy after femoral neck fracture is 2.5 years. The authors arrived at that number by performing statistical analyses on nearly 63,000 cases of femoral neck fractures treated with either modular unipolar or bipolar hemiarthroplasty. Patients were in their early 80s on average at the time of surgery. The researchers focused on revision rates because reoperations in this vulnerable group of patients typically yield poor results.
There was no between-group difference in overall revision rate within 0 and 2.5 years after the procedure. However, unipolar hemiarthroplasty was associated with a higher overall revision rate than bipolar hemiarthroplasty beyond 2.5 years after surgery (hazard ratio [HR], 1.86).
Farey et al. also drilled down into reasons for revision and found that unipolar prostheses had a greater risk of revision for acetabular erosion, particularly in later postoperative time periods. Conversely, bipolar hemiarthroplasty was associated with a higher risk of revision for periprosthetic fracture, which the authors surmise might have arisen from the greater range of motion (and therefore activity levels) permitted by bipolar implants.
Although the authors did not perform a formal cost-benefit analysis related to this dilemma, they observed a nearly $1,000 USD price difference between the most commonly used bipolar and unipolar prostheses. Farey et al. therefore propose that the more expensive bipolar prosthesis may be justified for patients with a life expectancy beyond 2.5 years, but that the unipolar design is justified for patients with a postoperative life expectancy of ≤2.5 years.
Click here to listen to a 15-minute OrthoJOE podcast about this topic, featuring JBJS Editor-in-Chief Dr. Marc Swiontkowski and OrthoEvidence Editor-in-Chief Dr. Mo Bhandari.
Click here to see a 3-minute Video Summary of this study.
Click here to read a JBJS Clinical Summary comparing total hip arthroplasty with hemiarthroplasty for displaced femoral neck fractures.
When Does I&D Beat 2-Stage Exchange in Second rTKA?
It’s hard to contemplate “conservative treatment” in the case of a revised total knee arthroplasty (rTKA) with extensive instrumentation that needs a reoperation due to periprosthetic joint infection (PJI), because all the treatment options in that scenario are pretty complex. In the January 6, 2021 issue of JBJS, Barry et al. report on a retrospective review of 87 revisions of extensively instrumented rTKAs that found that irrigation and debridement (I&D) with chronic antibiotic suppression was as effective as 2-stage exchange in preventing another reoperation for infection—and more effective in terms of maintaining knee function.
The average follow-up of the cases studied was 3.2 years, and the authors carefully defined “extensive instrumentation.” Among the 56 patients who were managed with I&D and suppression and the 31 who were managed with the initiation of 2-stage exchange (average age in both groups approximately 67 years), no significant differences were found in the rates of reoperation for infection or mortality. However, 9 of the 31 patients (29%) in the 2-stage group never underwent the second-stage reimplantation. Among those 9, 3 died prior to reimplantation and 2 underwent amputation due to failure of infection control.
Moreover, at the time of the latest follow-up, a significantly higher percentage of patients in the I&D group were ambulatory (76.8% vs 54.8% in the 2-stage group) and were able to functionally bend their knee (85.7% vs 45.2% in the 2-stage group). The authors surmise that these 2 findings are related to the soft-tissue damage and bone loss that typically occur during stage-1 removal of rTKA components.
Barry et al. conclude that in similar situations “deviating from the so-called gold standard of 2-stage exchange and accepting the modest results of I&D may be in the best interest of the patient,” as long as there are no loose implants in the existing construct. But the “sobering” mortality rates in the study (39.3% in the I&D group and 38.7% in the 2-stage group) remind us that this clinical scenario is extremely challenging for patients and surgeons, no matter which option is selected.
Click here to view an “Author Insights” video about this study with co-author Jeffrey Barry, MD.
Eschew Standard-Sized Heads When Revising THAs for Dislocation
No consensus has emerged yet regarding the best prosthetic construct with which to manage patients who require revision surgery for dislocation after a total hip arthroplasty (THA). But in the December 2, 2020 issue of The Journal of Bone & Joint Surgery, Hoskins et al. add insight into that question by tapping the Australian Orthopaedic Association Total Joint Replacement Registry to analyze which of 4 first-revision component constructs led to the fewest second revisions.
Among the 1,275 THAs that were revised once for prosthesis dislocation, 203 hips went on to have a second revision, with dislocation being the most common cause for re-revision. The authors studied the second-revision THAs in 4 prosthetic categories: standard-sized femoral heads, large-sized femoral heads, dual-mobility heads, and constrained acetabular liners. The rate of all-cause second revision was significantly higher in the standard-head group when compared with the constrained-liner group. But in the 91 cases of second revisions for dislocation, the standard head showed significantly higher second-revision rates than any of the other 3 constructs. There was no statistically significant difference in rates of second revision between those 3 non-standard articulations
The authors discuss dual-mobility heads at some length, asserting that “caution should be exercised in their routine use, particularly in younger and active patients.” They note that the constrained liner was the “only articulation to show a difference when compared with standard-head THA for both all-cause revision and revision for a subsequent diagnosis of dislocation,” but they observe that impingement and acetabular component loosening are common concerns with constrained liners.
Despite these caveats, it seems clear from this data that the choice of articulating surface for either a first or second revision THA due to dislocation should probably exclude standard head sizes. Calling for longer-term data on all 3 alternative constructs studied here (the follow-up periods were different for all 4 articulations), the authors emphasize that “surgeons should [also] look beyond articulating surfaces”—to surgical approach, component orientation, and patient factors such as soft-tissue quality—in the effort to reduce the burden of THA dislocations.
Antibiotic-Laden Cement Lowers TKA-Revision Rates in US Veterans
We recently celebrated Veteran’s Day with the annual tradition of rightfully honoring the men and women who have served in the Armed Forces. After their active duty ends, servicemembers are eligible for care in Veterans Health Administration (VHA) hospitals around the nation. The VHA is a “closed” medical system that affords ample opportunity for population-based research.
In the November 18, 2020 issue of The Journal, Bendich et al. utilized VHA data to compare revision rates after primary total knee arthroplasty (TKA) among veterans treated with antibiotic-laden bone cement (ALBC) or plain cement. Although results of similarly designed studies focused on this question have been equivocal, antibiotic-laden cement seems to be especially effective at preventing infection in higher-risk populations, which is what the US veteran population is considered to be.
The researchers identified 15,972 primary TKAs that were implanted using Palacos bone cement between 2007 and 2015. Approximately 70% (11,231) of those cases used cement mixed with gentamicin, while 30% (4,741) utilized plain bone cement. The authors found similar patient demographics among patients treated with ALBC and those treated with plain cement, but ALBC was used more frequently in patients with higher comorbidity scores.
Overall, utilization of ALBC increased from 50.6% of the cases in 2007 to 69.4% in 2015. At a follow-up of 5 years, ALBC TKAs had a lower all-cause revision rate (5.3%) than plain-cement TKAs (6.7%) and a lower rate of revision for infection (1.9% compared to 2.6%). Even after multivariable adjustments to account for patient, surgical, and hospital factors, these revision-rate differences remained.
Bendich et al. also found that 71 TKAs needed to be implanted with ALBC to avoid 1 revision TKA. With a cost differential of $240 per case for ALBC, I think spending $17,040 ($240 × 71) is more cost-effective than 1 revision TKA, although a formal cost analysis is warranted.
In the interest of full disclosure, as an active-duty US Air Force officer, I am inherently biased, but I feel that no cost is too great to improve the health of our veterans. The authors review arguments against using ALBC, such as a theoretical risk of poor cement mechanical properties and systemic toxicity, but the findings of this study suggest that cement with antibiotics enhances treatment outcomes among these US heroes.
Click here to view the “Author Insight” interview about this study with co-author Alfred Kuo, MD, PhD.
Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media
The Challenges of Complex Revision Elbow Arthroplasty
Lower-extremity joint replacement is quite well-advanced, thanks to a high incidence of disabling osteoarthritis and a 40-plus-year history of development in hip and knee prostheses. Additionally, during the last 5 to 10 years, we have made progress in prosthetic design and reliable surgical techniques for the ankle. In the upper extremity, we have a similar 4-decade development history with anatomic shoulder replacement and now 10-plus years with increasingly reliable reverse total shoulder arthroplasty.
However, techniques for elbow and wrist arthroplasty have been much slower to develop, due to lower incidence of pathology, the unique functional demands on these joints, and prosthetic-design and fixation issues. Still, the Conrad-Morrey family of implants has provided reliable elbow prostheses for more than 20 years. Meanwhile, the indications for elbow arthroplasty have narrowed to inflammatory arthritis and distal humeral fractures and nonunions in patients with lower functional demands. Unfortunately, failure of fixation, infection, and bone resorption do occur after primary elbow arthroplasty; consequently, a small but growing number of patients face revision elbow arthroplasty.
In the November 18, 2020 issue of The Journal, Burnier et al. report the results of revision elbow arthroplasty using a proximal ulnar allograft-prosthetic composite to compensate for missing ulnar bone stock and triceps tendon insufficiency. They clearly explain the surgical technique and report their results among a 10-patient cohort, including details of the 6 cases that required reoperation.
JBJS will continue reporting results of revision joint arthroplasty because members of the orthopaedic community have to manage these very complex cases, and this type of information is helpful to guide treatment decisions and patient expectations. Equally important is the positive impact this information has on further development of surgical techniques and prosthetic designs. Close examination of failure is the fuel for innovative improvement.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Complex Technology Demands Conflict-Free Reporting
In the October 7, 2020 issue of The Journal, Du et al. report on a multicenter database-derived cohort of 167 patients with early-onset scoliosis treated with traditional growing rods and followed for ≥2 years after “final” fusion. These researchers report that 19% of those patients required a repeat surgery following fusion, most commonly for surgical-site infection and anchor-site failure. Multivariate analysis of risk factors for reoperation following final fusion revealed the following:
- Curve progression requiring revision surgery during the spine-lengthening process
- The number of levels spanned with the growing rods
- The duration of treatment
Du et al. report these results without spin in a way that is most useful for surgeons who are considering using these implants in their armamentarium. This is the way all new technology, especially complex advances in surgical care, should be reported.
Orthopaedic implants and instruments continue to evolve, almost always toward more sophisticated digital technology, complex engineering, and more numerous moving parts. The advent of magnetic growing rods for treating early-onset scoliosis is just one example. Often such advances are reported on by surgeons who are conflicted by personal and financial interests in the technology. This leads to all manner of potential bias–indication bias, reporting bias, selection bias, and detection bias to name just a few. Readers should evaluate this type of data with a high degree of suspicion.
What we need throughout orthopaedics are more multicenter, multisurgeon, “deconflicted” cohort studies and clinical trials. When such rigorous studies are conducted to investigate “high-tech” growing rods in patients with early-onset scoliosis, I will not be surprised if researchers find the same risk factors for reoperation after fusion that Du et al. found.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Questions About Survival of Ultraporous Cups in THA
Acetabular components for primary total hip arthroplasty (THA) made with ultraporous surfaces were developed to enhance osseointegration and biological fixation. In the July 1, 2020 issue of The Journal of Bone & Joint Surgery, Palomaki et al. report on a registry study that suggests that implant survival with these components over an average follow-up of 3.6 years is not so “ultra.”
The authors evaluated >6,000 primary THAs that used a Tritanium ultraporous cup and >25,000 THAs that used a conventional cup, all performed between 2009 and 2017. When they compared the two groups for revision for any reason, the 5-year Kaplan-Meier survivorship of the Tritanium group (94.7%) was inferior to that of the conventional-cup group (96.0%). When revision for aseptic loosening was examined, the 5-year survivorship was also inferior for the Tritanium group (99.0%) compared with the conventional group (99.9%). Regression analysis revealed that the Tritanium group had a much higher risk of revision for aseptic loosening 2 to 4 years after surgery (hazard ratio, 11.2; p <0.001). Interestingly, these survivorship and risk-of-revision differences disappeared when the authors analyzed data for the period from May 15, 2014 to December 31, 2017–when the registry was updated to include patient BMI and ASA-class data.
The authors cite several caveats that readers should apply to these findings. The registry did not capture radiographic findings for these patients, so potentially relevant imaging data could not be analyzed. And, despite the database upgrade in 2014, there was a dearth of available data on patient comorbidities. Finally, wide confidence intervals for some of the hazard-ratio calculations suggest the need to confirm revision-risk findings with further research.
Limitations notwithstanding, the study by Palomaki et al. suggests that the performance of ultraporous cups may not meet the hopes and expectations of hip surgeons and their patients.
UKA: Alignment and Overhang Matter
(Reproduced, with permission, from Orthop Traumatol Surg Res. 2016 Apr;102[2]:183-7. Copyright © 2016 Elsevier Masson SAS. All rights reserved.)
These operations were performed by a group of fairly experienced surgeons who averaged >14 UKAs per year, although a commonly used threshold for a “high-volume” UKA surgeon is >15 procedures per year. The cumulative revision rate of 14.2% over 8.7 years, the 5-year Kaplan-Meier survival rate of 88%, and the 10-year survival rate of 70% found by Kazarian et al. are disturbing. Using revision as an endpoint may be problematic because some surgeons are quick to revise a UKA when the radiographic evaluation of component placement is not perfect. Still, this study demonstrates that radiographically determined alignment and overhang “outliers” and “far outliers” had a significantly increased risk of implant failure, compared with patients with good alignment and overhang.
This study did not include UKAs that used computer-assisted methods, but it seems safe to conclude that computer-assisted component placement would be more reliable than “eyeballing,” especially among surgeons with less-experienced eyes. Based on this and other recent studies, I think a controlled trial comparing the functional outcomes and revision rates of UKAs performed with and without computer assistance is warranted.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
Editor’s Note: Click here to read the JBJS Clinical Summary on Unicompartmental Knee Arthroplasty.
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